Organic & Biomolecular Chemistry Blog

Researchers in Switzerland have discovered a fluxional molecule that dynamically resolves to a single metastable structural isomer.

Bullvalene is an intriguing molecule. A small polycycle with 10 carbons and 10 hydrogens, and an unusual property: it has no permanent chemical structure.

Its bonds are constantly rearranging through a seemingly endless series of Cope rearrangements. It’s estimated that there are over 1.2 million possible valence tautomers, and due to the rapidity of the conversions, all carbons and protons appear as equivalent on the NMR timescale.

Professor Jeff Bode and his group at ETH Zürich have an interest in these fluxional molecules and their potential uses as chemical sensors.

During a recent investigation into the racemisation of oligo-substituted members of the bullvalene family, they noticed some interesting behaviour in a sample of a tetrasubstituted bullvalene. A single isomer was spontaneously forming, and could be isolated from the mixture. This isomer was surprisingly stable, with a half-life of just over 4 hours at room temperature.

Now, tetrasubstituted bullvalenes have 1680 possible structural isomers and previous work has shown that the mixture is fully dynamic, so the appearance of just one isomer above all the others is pretty remarkable.

Their latest HOT PAPER builds on these results, and seeks to provide further information about the nature of this fascinating molecule.

Expand this blog to read more…

Thanks to developments in new phosphine ligands the area of C–Cl bond activation has made a lot of progress.

In this paper Shengming Ma and colleagues at Zhejiang University report recent results of the Suzuki coupling reaction of optically active α-chloroalkylidene-β-lactones derivatives using a LB-Phos ligand previously developed by the group. Using this method Ma et al. have prepared a series of optically active α-alkylidene-β-lactones in high ee.

Do you think that this protocol is a versatile method for the organic community to utilise? Read the paper today and let us know by leaving your comments on this blog.

Pd-catalyzed Suzuki coupling reaction of chloroalkylidene-β-lactones with LB-Phos as the ligand
Pengbin Li, Bo Lü, Chunling Fu and Shengming Ma
DOI: 10.1039/C2OB26365C

Researchers from Taiwan have developed an efficient organocatalytic enantioselective synthesis of spironitrocyclopropanes.

In this HOT communication Wenwei Lin and co-workers from National Taiwan Normal University describe the development of an efficient asymmetric pathway for the preparation of spironitrocyclopropanes from 2-arylidene-1,3-indandiones and bromonitroalkanes, catalysed by cinchona-derived bifunctional organocatalysts.

Lin et al. report reaction conditions which allow almost perfect diastereocontrol as well as outstanding enantiocontrol. As nitrocyclopropanes are found in various biologically active natural products and important precursors of bio-relevant cyclopropylamines this new method fills a real synthetic need.

Want to know more? Read the communication for free now! And it will remain free for the next 4 weeks.

An efficient organocatalytic enantioselective synthesis of spironitrocyclopropanes
Utpal Das, Yi-Ling Tsai and Wenwei Lin
DOI: 10.1039/C2OB26943K

Chemists from University of Cambridge, UK, have constructed a new class of multicomponent [2] and [3]catenanes utilizing up to four building blocks and three orthogonal interactions.

A major challenge in supramolecular chemistry is being able to harness several orthogonal weak interactions to generate structures with a similar complexity and functionality to those found in nature. This is because, as the variety of the building blocks and noncovalent interactions involved, control over the final structure becomes exponentially more difficult.

In this HOT Communication Miguel Á. Alemán García and Nick Bampos report a one-pot synthesis which uses multiple supramolecular components with distinctly different sets of noncovalent interactions to construct heteroleptic interlocked supramolecular metallomacrocycles.

This Communication is free to access for the next 4 weeks!

Synthesis of a four-component [3]catenane using three distinct noncovalent interactions
Miguel Á. Alemán García and Nick Bampos
DOI: 10.1039/C2OB26587G

In this HOT paper Angel Vidal and co-workers at Universidad de Murcia discuss the conversion of N-(2-Substituted)aryl ketenimines into 3,4- dihydroquinolines. The reaction involves a 1,5-migration of a hydride or alkoxyl group, followed by a subsequent 6pi-electrocyclic ring closure.

Vidal et al. perform a detailed experimental study on the relative migratory aptitudes and activating effects of the 1,5- (H, RO, RS) shift / 6p-electrocyclic ring closure, and provide new interesting insights into the formation of highly substituted quinolones.

Want to know what the relative migratory aptitudes are? Or what has the best activating effect? Download the paper for free for the next 4 weeks!

1,5-(H, RO, RS) shift/6π-electrocyclic ring closure tandem processes on N-[(α-heterosubstituted)-2-tolyl]ketenimines: a case study of relative migratory aptitudes and activating effects
Mateo Alajarín, Baltasar Bonillo, Raúl-Angel Orenes, María-Mar Ortín and Angel Vidal
DOI: 10.1039/C2OB27010B

In this HOT communication Boris J. Nachtsheim and colleagues at Eberhard Karls University present preliminary results towards a fast and efficient synthetic approach of γ-spirolactams based on an iodine(III)-mediated oxidative spirocyclization of 2-(4-hydroxybenzamido)-acrylates.

In addition Nachtsheim et al. discuss the discovery of an unexpected side reaction, a rare iodine(III)-mediated spirocyclization that gave δ-spirolactones. With fluorinated solvents and modified reaction conditions this side reaction was able to produce δ-spirolactones in yields up to 70%.

Interested? Find out more about these reactions and their mechanisms by downloading this Communication for FREE.

A hypervalent iodine-mediated spirocyclization of 2-(4-hydroxybenzamido)acrylates – unexpected formation of δ-spirolactones
Christian Hempel, Nicole M. Weckenmann, C. Maichle-Moessmer and Boris J. Nachtsheim
DOI: 10.1039/C2OB26815A

In this HOT communication Marvin H. Caruthers and co-workers from the University of Colorado show that oligodeoxyribonucleotides bearing boranephosphonate linkages (bpDNA) are able to reduce a variety of metal ions whilst producing nanoparticles. Carauthers et al. discovered that during the reduction of metal ions in protic solvents, the B–P bond undergoes solvolysis and generates phosphate diesters (in water) or triesters (in alcohols).

To highlight the utility of this reaction Caruthers et al. synthesised an oligomer containing an O-methyl phosphate triester linkage, which cannot be prepared via usual methods of DNA synthesis as such triesters are base labile.

Caruthers et al. believe that, in addition to bpDNA‘s potential applications in the construction of DNA templated metallic nanostructures, the new reactivity of boranephosphonates shown can be exploited as a general method for the introduction of a variety of functionalities onto the DNA backbone via phosphate triesters.

Intrigued? Read this Communication for free for the next 4 weeks to find out more!

This Communication is part of the Nucleic acids: new life, new materials collection. Why not take a look at similar work and let us know what you think here on the blog or on Twitter.

Reduction of metal ions by boranephosphonate DNA
Subhadeep Roy, Magdalena Olesiak, Petra Padar, Heather McCuen and Marvin H. Caruthers
DOI: 10.1039/C2OB26661J